My Organic Dirt Patch: Cloudy and Cold with a Chance of Frozen Lettuce?

So I finally got some salad greens growing in my new organic garden. I was pretty proud of those little sprouts. The "Bright Lights" chard was looking good too. My doubting spouse still suspects it was a mistake to tear out the jasmine landscaping and plant these organic vegetables. So I dragged her out there the other day and pointed at the new growth. "See, see!" I said. "It's not going to be an ugly dirt patch much longer."

Then I heard the weather forecast. What are the odds my lettuce sprouts are going to survive a three-day hard freeze? Any suggestions from the gardening experts? Do I cover the bed with warm blankets? Water more or water less? Or do I go buy more seeds because my lettuce crop is S.O.L.?